The present teachings relate to an antireflection coating and a fabrication method thereof. More particularly, the present teachings relate to an antireflection coating that is corrosion resistant and a fabrication method thereof.
Diode pumped alkali lasers (DPAL) have been introduced and improved in the past decade, leading to the development of higher power DPALS with demonstrated power increase from a few milli-Watts to several hundred Watts. As power increases, optical damage to the sapphire window of DPAL has become a serious problem.
Deposits have been observed on the window coincident with the location of the laser beam. If the laser system is not turned off soon after the deposits appear, increased absorption can lead to catastrophic window failure. In addition, anti-reflection (AR) coatings that have been used to reduce the surface reflection have been found to rapidly degrade in the alkali environment, accelerating the aforementioned failure. Although the origin of the failure has not yet been fully understood, it appears that the failure comes about from a combination of the alkali vapor and the laser radiation. Two possible mechanisms are that (1) the laser light may be producing excited state rubidium, which is more aggressively attacking the windows, and that (2) the laser is heating the windows to a high temperature, accelerating the chemical reaction rates between the alkali and the window substrate.
Therefore, there is a need to develop new optical coating and substrate that are economic, durable, and manufacturable, so as to advance the state of the art in high-performance lasers.